Optimizing Mixture Components, Shiv Size and Content in Hempcrete for Thermal Capacitance

This study investigates the thermal performance of hempcrete, for use as the building envelope in masonry walls. Three samples of hemp hurds were sourced from Canadian harvests and a fourth from France. Each hemp hurds sample was cut to a different particle size distribution, and then incorporated at 5 binder-to-hemp ratios. Portland cement Type GU and hydrated lime were used in equal amounts to form the binder. The resulting mixtures were first tested for thermal conductivity and specific heat capacity. The experimental findings were then incorporated into an ANSYS based model, to predict the thermal energy stored and lost by each mixture when used as a building envelope for a masonry wall. The results show that while smaller hemp particles favour greater volume of interface, larger particles lead to higher porosity. In turn, they result in lower thermal conductivity, lighter hempcrete and hence higher thermal capacitance. Together, these properties result in higher thermal energy storage. The optimum thermal performance was obtained with hemp particles under 3 mm wide and shorter than 10 mm.